800 Jefferson Avenue, Suite B - Louisville, CO 80027 - (303) 673-9795 - (303) 673-9796 fax
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The Lower Boulder Creek stream restoration located immediately upstream of US Highway 287 in Boulder County, CO successfully restored 2,500 linear feet of Lower Boulder Creek which was channelized by the U.S. Army Corps of Engineers. The restored creek now has a natural stream configuration of a pool and riffle stream sequence. The project removed 3,000 cubic yards of sediment, re-using 2,000 cubic yards of the sediment to create 1 acre of persistent emergent wetlands in the now abandoned Corps channel. The stream length increased 450 feet adding 1/3 of an acre of instream habitat. These improvements provided significant public and environmental benefits and could not have been achieved utilizing the Corps configuration. As part of our design for the project, pools removed when the stream was straightened in the past were re-established in the new meander alignment. Streambanks were stabilized using Rosgen style rock vanes instream to manage the thalweg location away from the near bank region, allowing natural vegetative protection to be used on the side slopes. The design was based on techniques developed by Rosgen and were further complicated by the frequent manipulation of the upstream flows for irrigation, making the development of the bankfull flows a daunting task. This technique uses many factors to develop a stable cross section shape for each stream segment, and the use of a reference reach was made difficult due to the large area of disturbance that had previously occurred. The dimension, pattern, and profile for this stream reach was developed using elements from multiple areas and evaluating each for applicability to this design. Geomorphic design techniques were utilized to design the meander channel and extensive hydraulic modeling was undertaken to evaluate the flow conditions during larger flood events. This reach of Boulder Creek was purchased by Boulder County Parks & Open Space in 1994 as an open space/riparian corridor, floodplain storage area. This projects was sponsored by the Urban Drainage and Flood Control District (UDFCD) and Boulder County who together agreed to re-establish the stream stability and create both terrestrial and in-stream aquatic habitat to this degraded section of Lower Boulder Creek and to create new wetland/ riparian areas. Creative design and competent construction by Left Hand Excavating were combined to create a stable stream system that should require minimal maintenance in future years. |